1. Field the Invention
The present invention is directed to a rotary drill bit for well drilling, and more particularly, to a rotary drill bit having a single cutting head with a double cutting surface profile.
2. Description of the Prior Art
Prior art drill bits for well drilling include bits which do not have any moveable parts, such as fish-tail bits, wing bits and diamond bits, and tricone bits which have three separate rotatable conical elements mounted on corresponding legs with bearings and seals which are individually built. In tricone bits the legs are then welded to a body to form a single unit. The drill bits having no moveable portions have the disadvantage of drilling very slowly and the tricone bits have the disadvantage of rapid wear at high speeds and difficulty in repair because the cones cannot be removed without cutting the welds. Furthermore, tricone bits are only practical in larger sizes with a diameter of greater than 6 inches because of the need for large bearings.
Another entirely different type of prior art drill bit is the single conical cutting head Barnetche bit such as shown in U.S. Pat. No. 4,154,312 issued May 15, 1979, of which the present invention is an improvement. U.S. Pat. No. 4,154,312 is incorporated herein by reference. In a bit such as that described in U.S. Pat. No. 4,154,312 it is necessary to include a stabilizer on the side of the drill bit for absorbing the lateral load generated by the bit cone which is spread over a large surface. One of the problems encountered in bits of this type, is the wear which occurs on the bit stabilizer due to the large lateral load.